Substructures in Abell clusters of galaxies

31 Pages·2006·3.4 MB·English

A&A450,9–14(2006) Astronomy
DOI:10.1051/0004-6361:20041635 &
(cid:1)c ESO2006 Astrophysics
(cid:1)
Substructures in Abell clusters of galaxies
P.FlinandJ.Krywult
PedagogicalUniversity,InstituteofPhysics,ul.Swietokrzyska15,25-406Kielce,Poland
e-mail:[email protected]
Received10July2005/Accepted18November2005
ABSTRACT
Aims. WepresenttheresultsofsubstructuredetectiononalargesampleofAbellclusters.
Methods. Weapplythewavelettransformtopositionsofgalaxiesin183Abellclusters.Thesignificanceofthesubstructuringdetectedwas
determinedusingMonteCarlosimulationsonsetsof1000randomlygenerateddistributionsofgalaxiesforeachclusterandwaveletscale.
Results. 62 of the investigated clusters are strongly substructured; the frequency of occurrence of substructure is 0.34. The investigated
clusterswereclassifiedasunimodal,bimodalorcomplexsystems.Theclustersweredividedintoclustershavingsubstructuresinthefieldof
theclusterS orinthecoreregionS .TheKolmogorov-Smirnovtestshownosignificantdifferencesatthelevelα=0.05inthedistributionof
f c
clustershavingS andS substructureswithredshift.Usingaχ2 testwefoundnocorrelationbetweentheexistenceofsubclusteringandthe
c f
morphologicaltypeofgalaxyclusters.
Keywords.galaxies:clusters:general
1. Introduction of studied clusters had substructures in an aperture radius of
1Mpc.
The presenceorabsenceofsubstructuresin galaxyclustersis
The analysis of cluster ellipticity (Plionis 2002) revealed
very important for the study of cluster formation and evolu-
correlation with cluster redshift. Cluster ellipticity increases
tion. Over the past two decades, substructures have been de-
with redshift for the investigated sample with z < 0.18, see
tectedinasignificantfractionofgalaxyclusters.Theexistence
howeverFlooretal.(2003),Flinetal.(2004)andRahmanetal.
of subclustering suggests that clusters are dynamically young
(2004).
objects.Thisallowsonetotestcosmologicalmodels(Thomas
et al. 1998; Knebe & Muller 2000). The frequency of sub- By constructing radial number-density profiles for about
structuresinclusterswasusedin thepasttoevaluatethe den- 100clusters,Baier(1979,1983)andBaier&Mai(1977,1978)
sityparameterΩ (Richstoneetal.1992;Kauffmann&White concludedthatasmanyas80%oftheclusterstheystudiedhad
o
1993).Moreover,thepropertiesofgalaxiesinclustersdepend subclustering.Based on theprojecteddistributionofgalaxies,
on their environment. In clusters, morphology segregation is usingsurfacedensitycontourmapsfor65richgalaxyclusters,
found amonggalaxiesboth in substructuresand outside them Geller&Beers(1982)foundthatsubstructuresarestatistically
(Biviano et al. 2002). Similar results based on the APM clus- significantin40%ofthesecases.Thesamepercentageofsub-
ter sample were obtained by Plionis (2001). He found that in clustering was reportedby Dressler & Shectman (1988) from
the analyzed sample of data, dynamically young clusters are 3D data (radial velocities of galaxies). West et al. (1988) re-
spatiallymuchmoreclustered. portedalowerpercentageofsubclustering,findinglittlesignif-
Kolokotronisetal.(2002)investigatedasampleof22rich icantsubclusteringinthesamplestudied.Usingbothprojected
galaxy clusters, finding a strong correlation between the op- distributionsandradialvelocitiesof galaxies,West & Bothun
tical (APM) and X-ray (ROSAT) morphological parameters. (1990) foundstructuresintheouterpartsofclusters.Krywult
Theirworkledtotheconclusionthatinbothpartsofthespec- (1997)appliedthesymmetryandseparationteststopositional
trum it is possible to identify the dynamicalstate of a cluster data of 18 clusters and concluded that 32% of these clusters
correctly.Importantresults were obtainedby Schueckeret al. show substructures. Using a number of statistical tests on 33
(2001). Analyzing X-ray surface brightness distribution of clusters, Bird (1993) showed that depending on the method
470 clusters they found a substructure-density relation. 52% applied, from 10% to 40% have statistically significant sub-
structures. Escalera et al. (1994) applied the wavelet analysis
(cid:3) Tables1–3andFigs.3–17areonlyavailableinelectronicformat to16clustersclassifiedbythemasunimodalorbimodal.More
http://www.edpsciences.org recent studies were carried out by Kriessler & Beers (1997),
Article published by EDP Sciences and available at http://www.edpsciences.org/aaor http://dx.doi.org/10.1051/0004-6361:20041635
10 P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies
using the adaptive kernel technique for 56 clusters. They Sky Survey, which is the second source of our data. The es-
concluded that 57% of these clusters show substructures. A sentialdifferencebetweenthisandothersamplesisthevisual
wavelet analysis of 18 Abell clusters (Krywult et al. 1999) checking of all objects classified as galaxies when automatic
showed the existenceof substructuresin 50%ofcases. Using procedureswereapplied.
fourdifferentmethods,Krywult& Flin(2000)foundthatsta- We take into account only well separated Abell clusters
tistically significant subclustering is present in 40% of the with clearly visible galaxies, which allows us to perform the
investigatedclusters. visualverificationoftheautomaticstar/galaxyclassification.It
A comparison of our work with other recent studies indi- was performed for all objects brighter then m + 3 classified
3
catesagoodcorrespondencebetweenthefractionofsubstruc- bytheFOCASpackageasgalaxies,m isthemagnitudeofthe
3
tures detected in 2D and 3D data. Thus, the analysis of sub- thirdbrightestgalaxy.
structures in galaxy clusters based on projected, i.e. 2D data, Thesampleofgalaxyclustersanalyzedbyusisnotstatisti-
can reveal a statistically correct percentage of subclustering, callyuniform.However,weensurethereliabilityofstar/galaxy
disregarding some differences for individual objects (Flin & separation, which allows us to state that each of our clusters
Krywult2002). containgalaxiesonly.
Wepresenttheresultsobtainedfromalargesample,which Thebasicparametersoftheclustersincludedinthepresent
canbeusefulforcomparisonwithotherdata.Ourclusterscon- studyaregiveninTable1.Thefirstcolumncontainstheclus-
tainobjectswithinthestandard3magrangeanda visualver- tername,Cols.2and3givetherightascensionanddeclination
ificationofstar/galaxyseparationhasbeenperformed.Weuse (1950)ofthe cluster center,andCol. 3 showsthe cluster red-
theparametersh=0.75andq=0.5. shiftfromStruble&Rood(1987).Inouranalysis,wetookinto
ObservationaldataarepresentedinSect.2,withthemethod accountallgalaxieswithintheradiusofR=1.5Mpcfromthe
applied, i.e. the wavelet analysis, given in Sect. 3. Section 4 clustercenterandwith amagnituderangefromm3 tom3+3,
presentsthe results. In Sect. 5 we discuss the individualclus- wherem3isthemagnitudeofthethirdbrightestgalaxy.
ters.Section6providesaconclusion. The completenessof each galaxycluster sample has been
checked using the log(N) − m dependence. In all cases, the
completenesscoveredarangeofatleast3mag.For29ofthese
2. Observationaldata clusters Trévese et al. (1996)studied the luminosity function.
AsseenfromtheirTable1andFig.1,thesamplingwasdone
Therearetwosourcesofourdata.Thefirstisourpreviouspa- for M(cid:3) +2mag.ForclustersA157,A779,A2028andA2056
pers(Tréveseetal.1992,1997;Flinetal.1995;Flinetal.2000) themagnitudelimitwasbrighterthanm +3.Thiscanberelated
3
derived from 10-inch photographic plates taken with the 48- tothefactthattheautomaticstar/galaxyclassificationmethods
inch Palomar Schmidt Telescope (Hickson 1977). The emul-
break down for weak images of galaxieson the photographic
sions employed were Kodak 127-02 or Kodak 098-04, both
plates,ortothelowpopulationofgalaxiesintheclusters.
usedwitha2mmSchottRG-1glassfilter,whichcorresponds
to the red photographic F-bandof Oemler (1974). The plates
werecalibratedusingthePalomarspotsensitometer. 3. Waveletanalysis
The fields containing clusters originally selected by
Thedetectionofstructureintheregionsstudiedwasachieved
Hickson(1977),aswellassomeadditionalAbell(1989)clus-
byawaveletanalysis(Escaleraetal.1994).Thewavelettech-
ters clearly visible on the plates, were scanned in the trans- niqueis a convolutionon a grid of N × N pixelsbetween the
parencymodeusingaPDS1010Gmicro-densitometer,produc-
signal s(r) (inourcase,the angularpositionsofgalaxies)and
ingadigitalimageforeachclusterfieldwithapixelsizefrom
the analyzing wavelet function g(r,a). Following Escalera &
15 to 20 µm, accordingto the noise levelof the plate and the
Mazure (1992), we use the two-dimensional radial function
clusterdistance.Objectswereautomaticallydetectedandmag-
calledtheMexicanHat,givenbytheformula:
nitudevaluescomputedinmanycircularapertures,producing
(cid:1) (cid:2) (cid:1) (cid:2)
amagnitudeprofilefromwhichtheobjectswereautomatically r2 r2
classifiedaspoint-likeordiffuse. g(r,a)= 2− a2 exp −2a2 , (1)
Total magnitudes m were computed from the flux inte-
T
gratedinanapertureofradiusR = 1.5r ,wherer isthefirst where r is the distance between the position of a galaxy and
1 1 1 point (x,y) where the wavelet coefficient is calculated, and a
momentumofintensitydistribution(seeTréveseetal.1992).
is a scale length for the wavelet in order to form the corre-
Withthe abovedefinition,totalmagnitudescorrespondon
spondingsetofwaveletcoefficients.Asaresultoftheconvolu-
averagetothemagnitudem computedinacircularaperture
determinedbytheisophoteiµso= 24magarcsec−2,withthead- tion,thesignalistransformedintoasetofwaveletcoefficients
givenby:
vantage that r is less noisy than the correspondingisophotal
1
radius (see Flin et al. 1995). Magnitude-zeropointsare taken w(r,a)=g(r,a)⊗s(r). (2)
from the literature (Hoessel et al. 1980; Hoessel & Schneider
1985;Sandage&Perlmuter1991;Peterson1970;Gunn&Oke Eachpixelin the gridthen hasa correspondingwaveletcoef-
1975;Bothunetal.1985;Murphyetal.1983). ficient. Using a set of different scales, a structure is detected
Themajorityofgalaxycatalogueswereobtainedbyapply- only when its characteristic size is of the order of t√he scale
ing FOCAS package (Jarvis & Tyson 1981) to the Digitized applied.FollowingDaubechies(1990), the factorof 2 from
P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies 11
one scale to another ensures correct sampling in the case of 8
the Mexican Hat. When analyzed with the largest scale, the 7
field will produce a wavelet image showing a single central
6
structure. If the scale decreases, the central structure either
remains unchanged or splits into substructures. In this way, 5
we can detect all structures present in the map, irrespective
N4
of their location or size. For the analysis presented here, the
discrete wavelet was computed on a grid of 256×256 pixels 3
for seven scales increasing from a = 8 to 64 (in pixel units),
2
namely8,11,16,22,32,45,64,correspondingto94,129,188,
258,375,527,750kpc.Inordertoavoidanyedgeeffects,areas 1
largerthantheclusteritselfwereanalyzed. 0
0.0 0.05 0.1 0.15 0.2
z
We modeled the significance of the substructure detected
using Monte Carlo simulations. For each cluster and each Fig.1.Thedistributionofthegalaxyclusterswithsubstructuresversus
scalea,awaveletanalysiswascarriedoutonasetof1000ran- redshiftsforthemorphologicaltypeSc(solidline)andSf(dottedline).
domlygenerateddistributionsofgalaxiescontainingthesame
numberofpointsasintheactualfields.
Usingtheclassificationschemeforclustersofgalaxiesde-
Weassumethatasubstructureisrealiftheprobabilitythat
veloped by Rood & Sastry (1971) and by Bautz & Morgan
the detectedsubstructureis due to randomfluctuationsis less
(1970) the distribution of the clusters having substructures
than1%.Furthermore,foreachscaleaonlysubstructureswith
for different morphological types is presented in Table 2.
morethan4galaxymembersinacircleofradiusaareconsid-
Excluding results for types L and B, which are poorly popu-
ered.
lated,theχ2testshowsnocorrelationbetweentheexistenceof
In this way, we detected all structures in the field of the
subclusteringandthetypeofgalaxyclusteratthesignificance
galaxyclustersstudiedhere.FollowingEscaleraetal.(1994),
levelα=0.05.AlsotheS andS substructuresdonotdepend
weclassifiedthestructuresmorphologicallyaccordingtothree f c
ontheBMandRSclustermorphologicaltypes.
categories:unimodal,bimodalandcomplex.
WetestedifthedependenceS versusredshiftandS versus
c f
Some of the detected substructures are due to projection
redshiftis the same (Fig. 1). Using the Kolmogorov-Smirnov
effects.However,theapplicationof1000simulationsforeach testwedidnotfindanystatisticallysignificantdifferenceatthe
scaleaallowsonetoestimatetheprobabilityoftheexistenceof levelα = 0.05 between the distributions. The test carried out
thedetectedsubstructureintherandomdistributionofgalaxies,
forbinsof0.005,0.010and0.015leadtothesameconclusion.
anditissmall.Theoretically,subclusteringexistingin3Ddata
InFigs.3–18weshowonly62oftheclusterswithdetected
should be also detected in 2D data. However, it may happen
substructures.The plots show the distributionof galaxiesand
thattwosubgroupsarelocatedalongtheline-of-sight,thusap- thewaveletimagesonagridof256×256pixelsforsixwavelet
pearinginprojectionasonegroup.Theprojectioneffectis of scalesa=129,188,258,375,527,750kpc.Fromtheseplotsit
the same importance for clusters with and without 3D sub-
is possible to identify unimodalor bimodalclusters, and sub-
structures.Therefore,forthestatisticalinvestigationsofthefre-
structures.Ingeneral,thecentralA–structurecanstillbeseen
quencyofsubstructureoccurrencethisisnotaveryimportant
at small scales, althoughthe correspondingphysicalstructure
factor.
isclearlydefinedatthelargestscalesonly.
Thus, the wavelet analysis shows statistically significant
substructuresin34%oftheclustersinoursample.According
4. Results
to the frequency of clusters with statistically significant sub-
Theresultsofourwaveletanalysisappliedtothepresentsam- structures,theresultspresentedinthispaperareconsistentwith
ple of galaxy clusters are given in Table 3. Column 1 gives thoseofotherauthors,basedon2Dor3Ddata.
the cluster name, column2 identifiesthe structure(M – main
cluster;A –dominantcentralstructure;B, C–substructures),
5. Discussion
Col.3showsthewaveletscalesaatwhichthestructureswere
detected,withvaluesinpixelunitsforamapof256×256pix- Belowwepresentsomecommentsonsubstructuresinparticu-
els, Col. 4 gives the number of galaxies belonging to the rel- larclusters.
evant structures, and Cols. 5 and 6 show coordinates for the
center of the detected structure. Column 7 gives cluster mor- A76 – At the scales of a = 375kpc and a = 258kpc, this
phology(U–unimodal,Sf –substructurespresentinthefield clusterhastwogalaxygroupsintheclusterfield.
ofcluster,andSc –substructuresintheclustercore). A117 –Atthescaleofa=188kpcsubstructuresarelocated
Weassumethataclusterhassubstructuresinthecore(S ) inthecentralregionofthecluster.
c
if thedistancebetweenthecenterofthedetectedsubstructure A121 –Substructuresareidentifiedatscalesa=375kpcand
andthecenterofthemainclusterissmallerthan375kpc.Ifit a=258kpc.
islocatedatagreaterdistance,theclusterhassubstructuresin A133 –Inthisbimodalcluster,smallsubclustersoccuratthe
thefield(S ). scaleofa=188kpc.
f
12 P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies
A140 –Atthescalea = 188kpc,thisclusterhasonegroup A1809 – In this cluster the substructures are located in the
ofgalaxies. centralregionatthescalea=258kpc.
A151 – Two significant substructures at the scale a = A1831 –Thisclusterhastwosignificantsubstructuresinthe
375kpc. clustercenteratthescaleofa=188kpc.
A261 –Thisisbimodalclusteratscaleofa=527kpc. A1837 –Thesubstructuresarelocatedinthefieldoftheclus-
A358 –Substructuresexistsinthecentralregionofthecluster ter.
atthescaleofa=129kpc. A1904 –Thisclusterhasonesubstructureinthefieldatthe
A415–Twosignificantsubstructuresoccuratthescalesa = scaleofa=129kpc.
188kpcanda=258kpc. A1913 –Statisticalsignificantsubstructuresexistsatthescale
A426–Thesubstructuresarelocatedinthefieldofthecluster a=188kpc.
attheallscales. A1983 –Thisisabimodalcluster.
A496 –Thesignificantsubstructuresoccurattheallscalesin A2020 –Thisisabimodalcluster.
thefieldofthecluster. A2022 –Onegroupofgalaxiesatthescaleofa=129kpc.
A514 –Thisisanelongatedclusterwithsubstructuresatthe A2028 – In this elongatedcluster, substructureexists at the
scalesofa=375kpcanda=188kpc. scaleofa=258kpc.Itislocatedintheupperregionofthe
A527 –Onegroupofgalaxieslocatedattheexternalpartof field.
thecluster. A2052 –Thesubstructuresatthescalea=375kpcexistsin
A539 – At the scales a = 258kpc and a = 188kpc small theexternalregionofthecluster.
groups of galaxies are located at the central part of the A2065 – One group of galaxies in the external part of the
cluster. clusteroccursatthescaleofa=258kpc.
A548 – In this bimodal cluster, substructures exists at the A2073 – In this almost regularcluster, the wavelet analysis
scalesa=188kpcanda=94kpc. identified one substructure in the core region, at the scale
A671 – This cluster hastwo significantsubstructuresin the ofa=188kpc.
clustercenteratthescaleofa=129kpc.Eachofthemhas A2124 –Atthescaleofa=129kpc,twosmallsubstructures
8galaxymembers. arelocatedinthecentralregionofthecluster.
A754 –Atthescalesofa = 188kpcanda = 129kpcthere A2147 –Inthisclustertwogroupsofgalaxiesoccursatthe
arethreesubstructures. scaleofa=375kpc.
A786 –Onlyonesubstructureatthescaleofa=375kpc. A2151 –Thisisabimodalcluster.
A924 –Twogroupsofgalaxiesinthecentralregionofclus- A2152 –Thisbimodalclusterhassubstructureatthescaleof
ter,atthescaleofa=375kpc. a=258kpc.
A978 – In this symmetricalcluster two substructuresexists A2199 –At thescales ofa = 129kpc anda = 94kpcsub-
atthescaleofa=258kpc. structuresoccursinthefieldofthecluster.
A1016 –Atthescalea=188kpc,thisclusterhassignificant A2255 –Thiscluster hasonesignificantsubstructurein the
substructuresattheclustercenter. clustercenteratthescaleofa=129kpc.
A1060 –Therearesixsubstructuresatthescalesa=375kpc A2312 –Onesmallsubstructureinthecenterofthecluster,
anda=129kpc. atthescalea=188kpc.
A1187 – This bimodal cluster has two substructures at the A2457–Thisclusterhasonegroupofgalaxiesinthecenter,
scaleofa=527kpc. atthescalea=129kpc.
A1275 –Twosignificantsubstructureslocatedsymmetrically A2593 – Onlyone small groupof galaxiesis presentin the
accordingclustercenter. coreregionofthecluster,atthescaleofa=188kpc.
A1292 – One substructure at the outer part of cluster, a = A2877 –Onlytwosmallsubstructuresoccursatthescaleof
258kpc. a=94kpc.
A1367 – At the scale of a = 129kpc this cluster has two A3128 – In this cluster the substructures exists at all the
galaxygroups. scalessmallerthana=375kpc.
A1377 –Twosignificantsubstructuresoccuratthescalesof A3376 –Twogroupsofgalaxiesatthescalesofa=188kpc
a=129kpcanda=94kpc. anda=129kpc.
A1401 – Bimodal cluster, substructures at the scale of a = A3395 –Thisisthebimodalcluster.
527kpc. A3526 –Thisbimodalclusterhassmallsubstructuresatthe
A1413 – Thisisan elongatedcluster with twoclose groups scalesofa=375kpc,a=258kpcanda=188kpc.
ofgalaxiesatthescaleofa=375kpc. A3562 – Inthiscluster substructuresoccursatthe scalesof
A1631 – This cluster has substructures at the scale a = a=258kpcanda=129kpc.
188kpcintheclustercenter. A3667 – This cluster has significant substructures at the
A1650 –Thisclusterhassubstructuresintheclusterfield. scalesofa=258kpcanda=94kpc.
A1651 –Onegroupofgalaxiesatthescaleofa=375kpcin
thefieldofthegalaxies.
6. Conclusions
A1661 –Thiselongatedclusterhasonegroupofgalaxiesat
thescaleofa=375kpc. Themethodbasedonawavelettransformhasbeenappliedfor
A1736 –Thesubstructuresoccuratthescalesofa=188kpc. substructuredetectionintheprojecteddistributionsofgalaxies
P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies 13
112216932659202244668...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................a.......=.....5.......2......7......... 112216932659202244668...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................a.......=.......3.....7......5......... 112216932659202244668...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................a.......=.....2.......5......8.........
0 0 0
0 32 64 96 128 160 192 224 256 0 32 64 96 128 160 192 224 256 0 32 64 96 128 160 192 224 256
Fig.2. Distributionof galaxies inA85 withthe waveletimages for scalesa = 527,375,258 kpcpresented intheupper right box (galaxies
withinmagnituderangefromm tom +3).
3 3
in183Abellclusters.Thesignificanceofsubstructuredetected 587, the wavelet analysis showed some substructures, but
hasbeen calibratedusing simulateddistributionsbymeansof they are not statistically significant at our adopted probabil-
MonteCarlomodeling,performing1000simulationsforeach itylevel.However,whenallSlezaketal.(1997)datacovering
clusterandeachscale.ApplyingtheMexicanHatwaveletanal- a magnituderange much larger than m +4 were considered,
3
ysistotheprojecteddistributionsofgalaxiesin183clusters,we subclusteringwasdetected.
concludethatsignificantstructureispresentin62,thatis34% The influence of the cluster centre chosen has been ana-
ofthecases. lyzedforclustersusingmean,medianandACOcataloguecen-
Our results indicate that a large fraction of clusters have tres.Insomecaseswerefoundadifferencesbetweensubclus-
substructuresintheirprojectedgalaxydistributions.Acompar- teringbutthedifferencearenotstatisticallysignificant.
isonwithotherinvestigationsbasedbothontheprojectedand Insometeststodetectsubstructuresingalaxyclustersthere
on the3D data showsthat, whilein individualcases thereare isastrongdependenceontheclustercentrechoice.Thisisthe
sometimesdifferencesinfindingsubstructures,thepercentage case of the symmetrytest, the Lee test and others. A detailed
of substructure occurrenceis not greatly affected. We find no discussionisgivenusingnumericalsimulationsbyPinkeyetal.
correlationbetweenfrequencyof the clusterswith subcluster- (1996).
ingandtheirmorphologicaltype.
The wavelet analysis performs a convolution of the
OurresultsareinagreementwiththePlionis(2001)inves-
analysingfunction(e.g.MexicanHat)withpositionsofgalax-
tigation.Heappliedtwodifferentmethodsforsubstructurede-
ies in cluster regions. Contrary to previously mentioned tests
tection in 309 ACO clusters for which only about 180 have
thismethoddonotusethepredeterminedclustercentreforcal-
measured redshifts. In our studies all clusters have measured
culation.Ourearlierstudiesshowthatthechoiceofthecluster
redshifts,sooursamplesarealmostidenticallynumerous.
centreisanimportantfactorinfluencingthefrequencyofsub-
Theinfluenceofmagnitudelimitsonsubclusteringwasex-
structureoccurrence.
aminedbyFlin & Krywult(2000). Thiswas doneusingsym-
Our considerations also show that the percentage of sub-
metryandseparationtests(Westetal.1988).Thesubclustering
clusteringusingawaveletanalysisappliedto2Ddataisclose
dependsneitheronthemagnituderangeofconsideredgalaxies,
tothatobtainedfrom3Ddata.
whichism +2,m +3,andm +4,northepossibleerrorsin
3 3 3 In A496 the wavelet analysis shows one substructure lo-
determinationofthe thirdbrightestgalaxy.Theycheckedthis
catedintheouterregionofthiscluster.Durretetal.(2000)find
form +3,wherei=3...10.
i only small groupsof galaxies located in the central region of
This shows that the search for subclustering does not de-
the cluster, but no significant substructures. In Fig. 9 of their
pendonthemagnitudelimit,whenm +3orm +4isconsid-
3 3 paper there is one group of galaxies located in the outer re-
ered, butwhenthis magnituderangeis significantlyenlarged,
gion of A496, which correspondsto substructure detected by
substructurescouldbeobserved.
us. This comparison shows that different methods of analysis
We applied our method to published optical data (Slezak detectdifferentsubstructures.
etal.1997)oftheveryrichclusterAbell85(Fig.2).Thedata
The results presented in this paper are in agreement with
were analysed in the same manner as ours. We took into ac-
Burgettet al. (2004). They appliedfour statistical tests of the
count all galaxies within a radius of R = 1.5 Mpc from the
substructure analysis to the 25 low-richnessclusters from the
clustercentre.Tochecktheinfluenceofthemagnitudelimiton
2ndFGRScatalogueofgalaxyclusters.Theyconcludethatsub-
the detectedsubstructurestheanalysiswascarriedoutontwo
structures exist in 20% to 44% of clusters, depending on the
setsofcatalogues.Thefirstcataloguewasmagnitudelimitedat
methodapplied.
thelevelm +3,thesecondoneatthelevelm +4.
3 3
The results of a wavelet analysis show no statistically
significant substructures in neither case. Due to increases Acknowledgements. Wethanktheanonymousrefereeforusefulcom-
in the number of galaxies in this catalogues from 317 to mentswhichledtotheimprovementofthepaper.
14 P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies
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P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies,OnlineMaterialp1
Online Material
P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies,OnlineMaterialp2
Table1.Listofstudiedclusters.
Cluster α δ z Cluster α δ z Cluster α δ z
A14 0012.7 −2410 0.0640 A439 0327.5 +2437 0.1063 A1146 1058.9 −2227 0.141
A21 0017.9 +2821 0.0948 A449 0343.5 +7502 0.0803 A1185 1108.1 +2857 0.0304
A22 0018.2 −2559 0.1432 A465 0348.3 +0609 0.0855 A1187 1108.9 +3951 0.0791
A76 0037.2 +0630 0.0416 A496 0431.3 −1321 0.0320 A1190 1109.0 +4107 0.0794
A85 0039.1 −0937 0.0518 A500 0436.8 −2212 0.0666 A1213 1113.8 +2932 0.0468
A88 0040.4 −2619 0.1086 A505 0451.6 +7956 0.0543 A1216 1115.2 −0412 0.0524
A104 0047.1 +2415 0.0822 A514 0445.5 −2031 0.0731 A1228 1118.8 +3436 0.0350
A114 0051.2 −2157 0.0566 A526 0457.2 +0522 0.0541 A1275 1127.3 +3657 0.0603
A115 0053.3 +2603 0.1971 A527 0504.0 +7338 0.0794 A1292 1129.1 +3606 0.2319
A117 0053.5 −1018 0.0535 A537 0518.3 +7350 0.168 A1299 1129.7 +3415 0.2247
A119 0053.8 −0132 0.0440 A539 0513.9 +0624 0.2050 A1314 1132.1 +4919 0.0341
A121 0055.0 −0717 0.1048 A548 0545.0 −2538 0.041 A1334 1136.3 −0402 0.0555
A133 0100.2 −2204 0.0604 A564 0655.2 +6953 0.0779 A1346 1138.6 +0558 0.0970
A140 0102.1 −2414 0.152 A566 0659.8 +6322 0.0984 A1364 1141.1 −0129 0.1070
A147 0105.6 +0154 0.0438 A576 0717.3 +5550 0.0381 A1365 1141.8 +3111 0.0763
A151 0106.4 −1541 0.0526 A592 0739.9 +0929 0.0624 A1367 1141.9 +2007 0.0215
A157 0108.6 −1440 0.119 A637 0811.4 +4832 0.168 A1377 1144.3 +5601 0.0514
A166 0112.1 −1632 0.1156 A644 0815.0 −0726 0.0704 A1401 1149.5 +3733 0.1648
A168 0112.6 −0001 0.0452 A646 0818.6 +4716 0.1303 A1412 1153.1 +7345 0.0839
A189 0121.1 +0123 0.0335 A649 0820.6 +4902 0.150 A1413 1152.8 +2339 0.1427
A193 0122.5 +0826 0.0482 A655 0821.8 +4717 0.1245 A1437 1157.9 +0337 0.1339
A194 0123.0 −0146 0.0178 A671 0825.4 +3035 0.0494 A1474 1205.4 +1514 0.0791
A195 0124.2 +1855 0.0422 A680 0832.1 +3702 0.079 A1524 1219.2 +0807 0.1369
A260 0149.0 +3255 0.0348 A754 0906.4 −0926 0.0528 A1541 1224.9 +0907 0.0892
A261 0148.9 −0229 0.0467 A757 0909.4 +4755 0.0515 A1570 1233.9 +2005 0.180
A262 0149.9 +3554 0.0161 A779 0916.8 +3359 0.0226 A1589 1239.1 +1852 0.0718
A274 0152.2 −0631 0.1289 A786 0923.7 +7501 0.1241 A1630 1249.2 +0450 0.0649
A277 0153.3 −0737 0.0947 A924 1004.1 +3554 0.0989 A1631 1250.2 −1510 0.0508
A278 0154.4 +3159 0.0896 A978 1018.0 −0616 0.0527 A1644 1254.6 −1705 0.0449
A279 0153.8 +0049 0.0797 A979 1017.9 −0738 0.055 A1650 1256.2 −0129 0.0845
A358 0227.8 −1325 0.0576 A1016 1024.4 +1114 0.0321 A1651 1256.8 −0355 0.0825
A389 0249.1 −2507 0.1160 A1035 1029.2 +4028 0.0799 A1661 1259.4 +2921 0.1671
A399 0255.2 +1249 0.0715 A1060 1034.5 −2716 0.0114 A1675 1302.9 +3449 0.184
A401 0256.2 +1323 0.0748 A1081 1042.0 +3550 0.1588 A1689 1309.0 −0106 0.181
A407 0258.6 +3538 0.0470 A1126 1051.3 +1707 0.0852 A1691 1309.1 +3928 0.0722
A415 0304.4 −1214 0.0788 A1132 1055.3 +5703 0.1363 A1700 1312.3 +2859 0.142
A426 0315.3 +4120 0.0183 A1139 1055.5 +0146 0.0383 A1736 1324.1 −2651 0.035
P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies,OnlineMaterialp3
Table1.continued.
Cluster α δ z Cluster α δ z Cluster α δ z
A1749 1327.3 +3753 0.059 A2073 1523.6 +2835 0.120 A2457 2233.2 +0113 0.0597
A1774 1339.0 +4016 0.1691 A2089 1530.6 +2811 0.0743 A2593 2322.0 +1422 0.0433
A1775 1339.6 +2637 0.0696 A2092 1531.3 +3119 0.0669 A2597 2322.7 −1223 0.0852
A1795 1346.7 +2650 0.0616 A2096 1533.5 +3730 0.134 A2634 2335.8 +2645 0.0312
A1809 1350.8 +0524 0.0788 A2107 1537.6 +2156 0.0421 A2657 2342.3 +0852 0.0414
A1831 1356.9 +2814 0.0733 A2124 1543.1 +3613 0.0654 A2665 2348.2 +0550 0.0556
A1837 1359.1 −1055 0.0376 A2142 1556.2 +2722 0.0899 A2666 2348.4 +2652 0.0265
A1904 1420.3 +4847 0.0708 A2147 1600.0 +1602 0.0356 A2670 2351.6 −1041 0.0745
A1913 1424.5 +1654 0.0533 A2151 1603.0 +1753 0.0371 A2700 0001.3 +0147 0.0978
A1927 1428.8 +2553 0.0740 A2152 1603.1 +1635 0.0374 A2717 0000.7 −3614 0.0498
A1942 1436.1 +0353 0.224 A2175 1618.4 +3002 0.0978 A2721 0003.6 −3500 0.114
A1983 1450.4 +1657 0.0441 A2197 1626.5 +4101 0.0303 A2877 0107.6 −4610 0.0241
A1991 1452.2 +1850 0.0586 A2199 1626.9 +3938 0.0303 A3128 0328.8 −5244 0.0554
A2020 1501.3 +0807 0.0578 A2210 1632.3 +0535 0.1465 A3266 0430.5 −6135 0.0594
A2022 1502.2 +2837 0.0564 A2255 1712.2 +6409 0.0800 A3376 0559.1 −4003 0.0455
A2028 1507.1 +0743 0.0772 A2256 1706.6 +7847 0.0601 A3391 0625.2 −5339 0.0531
A2029 1508.5 +0557 0.0767 A2311 1850.2 +7019 0.0675 A3395 0626.5 −5422 0.0498
A2040 1510.3 +0737 0.0456 A2312 1853.8 +6818 0.0590 A3526 1246.1 −4102 0.0110
A2048 1512.8 +0434 0.0945 A2315 1901.2 +6953 0.0822 A3558 1325.1 −3114 0.0482
A2052 1514.3 +0711 0.0348 A2319 1919.2 +4352 0.0564 A3562 1330.7 −3125 0.0499
A2055 1516.3 +0623 0.0530 A2366 2140.2 −0706 0.0542 A3667 2008.5 −5658 0.0530
A2056 1517.1 +2827 0.0763 A2384 2149.5 −1947 0.2384 A3716 2047.9 −5254 0.0456
A2063 1520.6 +0849 0.0337 A2399 2154.9 −0802 0.0587 A3888 2231.5 −3759 0.1680
A2065 1520.6 +2754 0.0721 A2410 2159.4 −1008 0.0806 A4038 2345.1 −2825 0.0283
P.FlinandJ.Krywult:SubstructuresinAbellclustersofgalaxies,OnlineMaterialp4
Table 2. The frequency of the galaxy clusters with significant sub- Table3.Resultsofthewaveletanalysis.
structuresversusthemorphologicaltype.
Cluster Struct. a–Scale X Y N Morph.
c c gal
Morphology Total Clusterswith Frequency A14 A 64 124 138 95 U
number substructures A21 A 64 110 126 31 U
cD 47 13 28 A22 A 64 130 106 89 U
C 35 12 34 A76 A 64 121 134 43 S
f
B 12 1 8 45 107 139 24
I 38 7 18 B 32 94 153 14
F 31 14 45 156 120 13
L 12 5 42 C 22 155 120 10
95 177 10
16 152 118 6
11 91 119 5
A85 A 64 109 117 119 U
A88 A 64 95 129 22 U
A104 A 64 110 109 62 U
A114 A 64 137 106 52 U
A115 A 64 109 184 59 U
A117 A 64 105 154 37 S
c
45 90 158 21
32 79 161 13
22 79 162 10
B 16 78 162 9
C 158 114 6
11 78 162 9
8 78 163 8
A119 A 64 129 139 64 U
A121 A 64 127 123 53 S
f
45 39 194 33
B 32 36 197 19
C 22 192 131 12
33 198 13
16 192 131 12
11 191 131 8
8 190 130 5
A133 A 64 121 135 81 B,S
c
A1 45 111 138 55
A2 213 39 46
32 107 138 42
216 36 28
22 97 149 25
123 123 20
223 38 15
B1 16 127 121 18
B2 95 155 16
11 126 122 10
8 126 124 7
A140 A 64 106 109 76 S
c
45 100 109 47
32 92 108 31
22 82 100 16
B 16 79 97 13
11 78 97 9
8 79 98 6
A147 A 64 182 119 43 U
A151 A 64 111 118 48 S
f
45 110 128 35
B 32 122 127 23
C 125 26 17
22 127 128 14
119 29 12